#include <stdio.h>
#include <unistd.h>

int g_val=100;

int main()
{
    pid_t id=fork();
    if(id==0)
    {
        int n=0;
        while(1)
        {
            printf("I am child. pid: %d, ppid %d, g_val: %d, &g_val: %p\n",\
                    getpid(),getppid(),g_val,&g_val);
            sleep(1);
            n++;
            if(n==5)
            {
                g_val=200;
                printf("child change g_val 100 -> 200 success\n");
            }
        }
    }
    else
    {
        while(1)
        {
            printf("I am father. pid: %d, ppid %d, g_val: %d, &g_val: %p\n",\
                    getpid(),getppid(),g_val,&g_val);
            sleep(1);
        }   
    }
    return 0;
}
